As you can see, most of the ocean doesn't even see sunlight. Even
scientists aren't familiar with everything that's down there.

In fact, getting to the deepest reaches of the ocean is so
expensive that some people —
like Oscar-winning director James Cameron — take it upon
themselves to explore underwater spaces rarely visited by humans.

Cameron visited the Mariana Trench, the deepest place on earth at
seven miles below the surface of the Pacific Ocean, in a
minisubmarine in 2012. He was only the second person to visit
that area of the ocean.